Deliming hides with citric acid fermentation liquor



Patented May 26, 1953 DELIMING HIDES WITH CITRIC ACID FERMENTATIONLIQUOR Hermann Rudy, Heidelberg, Germany, assignor to Job. A. Benckiser,G. in. b

. H., Chemische Fabrik, Ludwigshafen (Rhine), Germany No Drawing.Application September 19, 1951, Se-

rial No. 247,370. In Germany April 6, 1950 4 Claims.

This invention relates to a process for removing lime and otheralkalies, such as sodium sulfide, and to deliming baths and delimingcompositions useful therein. More particularly the application relatesto deliming processes, deliming baths and deliming compositionsutilizing unrefined citric acid.

Up to the present time it has been the customary practice to delimehides or skins which have had their hair removed and their epidermalsystem separated from the true skin by using alkalies, such as lime andthe like, in deliming baths containing acidic deliming agents, forexample, inorganic acids, such as hydrochloric acid, sulfuric acid,boric acid, and the like; or organic acids, such as formic acid, aceticacid, lactic acid, 'butyric acid, and the like. This method, however,has the disadvantage that under the action of the acid ions, especiallywhen more deliming agent is present than required, the pelts are greatlyswollen whereby the quality of the leather made from the hides isconsiderably impaired. Such an undesirable effect may be diminished bypartially neutralizing the acids with ammonia, but then a comparativelylarger quantity of the partially neutralized acid will be necessary toseparate the lime.

Ammonium salt deliming agents have also been suggested for deliminghides and skins including ammonium salts of inorganic and organic acids,such for example, as ammonium sulfate, ammo nium lactate, ammoniumtartrate, ammonium citrate, and the like. The relatively small delimingeffect and the high price of such salts restricts their general use.

Thus, it has been a long standing problem to find a suitable delimingagent which will have a good deliming effect without deteriorating thepelts and which, at the same time, is sufficiently low in price towarrant widespread use.

It is an object of this invention to provide a deliming process,deliming baths and deliming compositions which overcome or greatlyalleviate the above mentioned disadvantages. Other objects andadvantages of the invention will be apparent from the more detailedfollowing description.

In accordance with this invention it has been found that an unrefinedcitric acid obtained by the fermentation of carbohydrate compounds withmicroorganisms, such as molds, show an excellent deliming effect withoutcausing the animal hides to swell and can be produced at relatively lowcosts. For the purposes of this invention unrefined citric acid producedby fermentation of carbohydrates is to be understood to mean thefermentation liquor produced in the Well known citric acid fermentationprocess or compositions containing the active ingredients of suchliquor. This liquor is also identified by the term citric acidfermentation liquor. It consists of the unrefined citric acid producedby the well known fermentation process and the liquid medium, or citricacid waste fermentation liquor in which the citric acid has beenproduced by such a process. The process of producing it is described,for instance, in Chemical Activities of Fungi by Jackson W. Foster(Academic Press, New York, 1949) on pages 385 to 386. It is the productof the culturing of a citric acid ferment, such as Asperyillus niger,for a period of days in an acidic molasses medium containing nitrogenousmatter and inorganicnutrient salts, and it generally contains about 10to 15% of citric acid.

While we do not wish to be limited by any theory, it is believed thatthe advantages of the present invention are due, in part at least, tothe fact that the citric acid fermentation liquor has a combineddeliming and antiswelling effect. In view of the fact that it is notnecessary to neutralize the citric acid content of the citric acidfermentation liquor, only a very small quantity of the liquor per unitof dry material is required. Normally a deliming bath will require onlyabout 1.5% of the citric acid fermentation liquor althoughconcentrations of the order of 0.3% to 2. may be used in such baths. Itwill also be understood that equivalent quantities of concentratedcitric acid fermentation liquor may be used instead of the citric acidfermentation liquor produced in the fermentation process.

In accordance with one embodiment of the invention the citric acidfermentation liquor is mixed with additional Waste fermentation liquorsremaining after the citric acid content has been removed from theunrefined fermentation liquor. The added waste fermentation liquorsserve not only to dilute the citric acid fermentation liquor but toexert a further complementary action when used in deliming baths. Suchwaste liquors. may be obtained advantageously by precipitating thecitric acid content of a citric acid fermentation liquor as calciumcitrate, and then separating the precipitate from the mother liquorthereby leaving the waste fermentation liquor. The fermentation liquorpresent with produced citric acid, or remaining after the separation ofthe citric acid content or compositions containing the activeingredients thereof, are referred to herein as citric acid wastefermentation liquor. If desired, the deliming baths having appropriatestrength of unrefined citric acid for deliming purposes may be obtainedby diluting the unrefined acid entirely with Waste fermentation liquorsor by diluting it partially with waste fermentation liquors andpartially with conventional" dil'u-nts such as water. The wastefermentation liquors left after the separation of citric acid producedby the fermentation of molasses, such as molasses separated in sugarrefining, has proven especially advantageous.

Of course, it will be understood that in the practice of this inventioninstead of using "unrefined citric acid produced. by thefermentation ofcarbohydrates corresponding quantities of refined citric acid may beused together with quantitles of citric acid waste fermentation liquorsnormally present in the unrefined citric acid.

It has also been found advantageous to. produce deliming compositions bydiluting and complementing the unrefined citric acid with liquorsobtained after the separation of tartaric acid or salts of tartaric acidfrom their unrefined solutions during the refining process. Tartaricacid may be separated from wine lees, for example, by convertingtartaric acid or salts thereof to calcium tartrate, dissociating thecalcium tartrate into tartaric acid, and recovering the tartaric acid bycrystallization. Such liquors left after the recovery of tartaric acidor compositions containing the active ingredients thereof are calledherein tartaric acid waste liquors. The unrefined citric acid maybediluted to a strength suitable for deliming purposes by adding citricacid waste fermentation liquors in combination with citric or tartaricacid waste liquors. When the deliming bath is diluted with either ofthese waste liquors, and especially when mixed with both types of wasteliquors, the deliming composition exerts both a delir'ning'and batingeffect.

It is possibIe also to add the unrefined citric acid of this inventionto known bating baths, particularly to synthetic leather bates, wherebyboth a deliming and hating take place.

The unrefined citric acid of this invention may be used, if desired,conjointly with other organic acid deliming agents, for example, lacticacid, acetic acid, tartaric acid, or with deliming ammonium salts, suchas ammonium sulfate, ammonium tartrate, ammonium lactate, and ammoniumcitrate, or with deliming polymeric polyphosphates and the like.

The great economic advantage of using unrefined fermentation liquorscompared with the utilization. of known organic acid or organic saltdeliming agents produced by fermentation is apparent, as the expenseinvolved in the separation of the active deliming components of suchfermentation masses is avoided. The separation of the active delimingcomponents, in accordance with prior art practice, may involve, forexample, (1) the production of the calcium salt (2) the decomposition ofthe calcium salt by sulfuric acid and (3) crystallization and separationof the pure acid. When the unrefined citric acid is used, as in thisinvention, all such additional expenses are avoided.

It is surprising that the fermentation liquors, including the citricacid, can be used without further refinement as deliming agents, for itis known that calcium citrate is a very slightly soluble salt. Thus itwould be expected that the reaction of the unrefined citric acid withcalcium compoundsas in deliming, would result in the formation of a veryslightly soluble precipitate '4 which would be formed in the hide,resulting in leather damage, as is true when such salts are formed intanning operations. This surprising result may be attributed to unknownattributes of the fermentation liquors associated with the citric acid.

In accordance with the present invention, therefore, very satisfactorydeliming agents are provided at an acceptably low price while agentsheretofore known were either too costly or unsatisfactory.

The following examples further illustrate the practice of-the invention.

Example 1 Goat skins were soaked and washed in a cask for ashort timeafter liming. The goat skins were then introduced into a deliming bathcontaining1.5% of an unrefined citric acid. The unrefined citric acidconstituted a fermented liquor containing 15% citric acid. Deliming tookplace very quickly. The pelts had an especially smooth feel, and theglazed kid made therefrom had an especially fine grain.

Example 2 A calf skin limed and washed as usual was introduced into asolution containing 10 grams of unrefined citric acid and 3 grams ofammonium sulfate per liter and it was delimed in the solution until asample of the pelt was free of lime. The process took nearly an hour.Then the skin was bated and worked up to box calf in the usual manner.The resulting leather showed an especially fine and smooth grain.

Example 3 An unrefined citric acid was produced by fermenting acarbohydrate with Aspergillus niger and 10 parts thereof were dilutedwith parts of citric acid waste fermentation liquors obtained in theproduction of refined citric acid. The resulting solution formed asuperior deliming bath for cow hides being processed for sole leather.During the deliming operation additional unrefined citric acid was addedto maintain its concentration in the bath at about 2%.

While the practice of the invention has been exemplified hereinbefore byreference to various details and examples, it will be understood thatthese may be varied widely and substituted by equivalents withoutdeparting from the substance of the invention as herein disclosed andclaimed.

What is claimed is:

1. A process for deliming hides and skins which comprises contacting thehides in the limed condition with a solution containing approximately0.3% to 2.0% of citric acid fermentation liquor.

2. A process for deliming hides and skins which comprises contacting thehides in the limed condition with a solution containing approximately0.3% to 2.0% of citric acid fermentation liquor for a period of theorder of one hour.

3. A process for deliming hides and skins which comprises contacting thehides in the limed condition with a solution containing approximately0.3% to 2.0% of citric acid fermentation liquor produced by thefermentation of molasses, said liquor containing about 15% of citricacid.

4. A process for deliming hides and skins which comprises contacting thehides in the limed condition with a solution containing approximately0.3% to 2.0%01? a commercial citricacid fermen 6 tation liquor and alesser quantity of ammonium Number Name Date sulfate. 1,772,258 Le PetitAug. 5, 1930 HERMANN RUDY. 2,132,579 Rohm Oct. 11, 1938 References Citedin the file of this patent 5 N b EOREIGl: PATENTS t um er Coun ry Da. eUNITED STATES PATENTS 1,049 Great Britain 1852 Number Name Date 5,620Great Britain of 1893 y g 59% 12;: 266,414 Great Britain of 1926 e mer*e 873,074 Nowak Dec. 10, 1907 OTHER REFERENCES 996,509 Nowak June 27,1911 Basu et ails-abstract in Journal Int. Soc. Lea. 1,570,383 McCandishJan. 19, 1926 Trades Chem. March 1948, page 109.

1,679,186 Szucs July 31, 1928

1. A PROCESS FOR DELIMING HIDES AND SKINS WHICH COMPRISES CONTACTING THEHIDES IN THE LIMED CONDITION WITH A SOLUTION CONTAINING APPROXIMATELY0.3% TO 2.0% OF CITRIC ACID FERMENTATION LIQUOR.